Amplifier



July 19, 1932.` s, rLOEWE 1,867,577

AMPLIFIER Filed Nov. 11, 1926 TORNEY Patentes July 1,9, i932"- UNITED STATES PATENT', oFFlca 110m 0l' BERLIN, FRIEDENA, GERMANY, ASSIG-NOR TO RADIO PORLTION 0F AIEBIGA, A CQBPOBATION 0F DELAWARE ACun.-

Applleation Sled Iovember 11, 1898, Seria! No. 147,843, andin Germany November 12. 1925.

' rEllis invention relates to an amplifier, and more particularly to `an `amplifier using both hot and coldcathodes. The roblem of making' electronic tubes 5 with co d cathodes is, fundamentally speaking, feasible and solvable in various ways. For exam le, the use of radio-active substances, p oto-electrically active surfaces, chemical combinations exhibiting slowly prow ceeding reactions, metallicalloys of emissivity, and the like, would alord able schemes.

However, it has been found diiiicult to produce, by means of cold cathod, electron '15 currents of a strength, suliicient for thev sustained, strong operation of a telephone on loud-speaker. Such currents must be of an' order of magnitude of several milliamperes; whereas,the lar st currents that can be proau duced with col cathodes are smaller; that is to say, of a magnitude insucient to operate a. loudspeaker.

It is an object of this invention to provide an amplifier, in which one or more cold elecz5 tron emittinglsources may be used, for the operation ofv relatively large current-drawing devices.

If it is'nlot possible to obtain the com-` aratively high electronic .emissions re ired 1n the last stage of a receivingampli er or tural simplification of the tubes and receiving equipment is considerable. This will be yfurther explained below.- l

Another obect of this invention is to cause, either directly or indirectly, the electron-emission of the cathodes of the first few. stages bv the phenomena occurring in the last stage. is may be explained as follows: Since, in the first stages about one-hundredth of the emission is required which tkhe any other arrangement of the present kindA last power stage has to deliver for the operation of the telephone or the loud-speaker,

`it is sulicient to branch oif a small lraction` ofthe emission of the-last heated cathode in order to run thereby the preceding amplifier stages. Especially in the case of -what is known. as multiple-unit systems where the iii-st stages and the finalstage-are enclosed 1n the same vacuous space, it .is possible to thus obtain more far-reachingresults.

The emission in thepreceding stages may be accomplishedby using the luminous effect of the last hot tube.'l That is, by the utilization of photo-electric effects, the small requisite emission is obtained. This scheme is very g5 practicable in the case \of tube systems bui-1t and assembled inV a common vacuous space, and it may also be applied to separately mounted tubes. 'l A very faint light such as that of dull oxide cathodes is suiiicient toproduce an appreciable photo-electric electron-emission. If daylight is available in the iirst sta es, and if. these stages are photo-electrical y excited, this natural sourceof light will, in eneral,- prove adequate. `But when such tu es are encased, so that light is excluded, for the constant maintenance of photo-electric effects in the preceding stages, it is possible to take' advantage of Vthe luminous eect Which the so thermo-electricall ,operated last stage will produce and whic heretofore has been of no use whatever. l It will be evident that by ananalogous application ofthe basic idea, it is also posy sible toutilize the thermal radiation of the incandescent cathodeA for the thermo-electric release .of the small volumes of electrons that are required in the preceding stages or systems. 9u My invention, which willbe explained and described by the aid of a multiple-unit system built into an evacuatedvessel, will illustrate an application of the preceding general ideas. In ythe drawing, Figure 1 represents 95 an amplifier wherein the electron emission from a preceding stage is caused by light falling upon the cathode of that stage;

Figure .2 shows .a modification wherein such an electron emission may be caused by 10e the emission of light and electrons from the cathode of an end stage.

Referring to Figure 1, 1 indicates a glass vessel in which two multiple electrode ampli- '1 fier systems each comprising a cathode have been placed. The lower system represents the final stage,`which, according to this invention, is to be worked theremo-electrically. 2 is the filament or cathode of this system, the filament being, for instance,` of the hairpin pattern. The grid or control electrode is indicated at 3, and the cylindrical anode or plate is denoted by 4. 'I'he upper system comprises a cold cathode which is indicated by a cylinder 5 which may be connected singlepole fashion with the filament 2 by con` nector 21. The surface of this cylinder shall be assumedto be photo-electrically active. The cylinder may be coated with thallium, suliite, potassium hydride, selenium, rubidium or the like. It receives its photo-electric energy by means of the light or heat radiation issuing from filament 2. In this case the emission is effected by photo-electric means. The re-supplyof electrons is effected through the connecting lead 21 with the heated cathode. About the body 5 may be wrapped a control element 6, while the entire system is enveloped by a likewise cylindrical anode or plate 8. Of course, the anodes, or part thereof, may be made of Wire auze or` lattice or may otherwise be perorated or apertured in order that, if necessary, sufficient lightmay be admitted, The interior of the glass wall 1 may be coated with a reflecting surface 1. There will then be such a complete reiection of the light from all sides of the glass wall that the photo-electrically active .surface 5 is always sufficiently illuminated as long as the filament 2 is incandescent. Of course, if the filament 2 burns at dull incandescence photoelectric substances will preferabl be chosen which are predominantly sensitive to long wave luminous rays. If the filament burns brighter, photo-electric substances sensitive to the radiations of shorter wave-lengths should be chosen.

The systems can be used in any desired manner. For example, the grid 6l may have a lead-in at 7. The plate 8 may be connected by way of a high-ohmic resistance 9 dis osed inside the tube through a lead-in 10 wit the n plate battery or else directly with the plate 4 in which latter case the lead-in or seal can be dispensed with.' The grid 3 ris united through a stopper or block condenser 11 with the plate 8. The lead for plate 4 is brought out at 12 andl carries the controlled power current for the operation of the consuming or working device connected in the rear of the tube. t

The arrangement hereinbefore described can be vused for radio frequency or low frequency amplification. The control currents are fed in between lead 7 and the lead '13. They control the system 5, 6, 8 working with a cold cathode according to this invention, the ensuing alternating potentials being transferred by way of condenser 11 to the grid 3. By means of these control potentials the power tube 2, 3, 4, is controlled. It is evident that in lieu of the two systems here shown by way of example, a greater number thereof could be assembled Within the same vacuous space. In this case the cold photo-electric cathodes ofthe first stages or multiple electrode systems each comprising an anode and a cathode could be excited in the same manner as described in connection with Figure 1 for the system comprising elements 5, 6, 8.

Figure 2 illustrates another sort of a combination composed of cold and incandescent cathodes. In this case, a straight filament 14 is employed which is enveloped by a grid 15 and a plate 16 diagrammatically indicated. The plate could likewise consist of wire gauze or netting. 14, 15, 16 is the power triode or multiple electrode system operated thermionically, and constituting Ithe end stage or end triode system. There is further disposed inside the tube the cold cathode 17 which is covered up by an apertured grid 18, and a plate 19. The system 14, 16'delivers part of its electrons into the surrounding space. These are collected by the cathode 17 and cause the issuance of secondary eleetrons which are controlled by the grid 18 and are led off by plate 1'9. This action can be further assisted i'f, for example, the cathode 17 is united by way of a low-potential source 20 supplying a few volts to one end of the filament 14. The power to be amplified to a slight extent is fed to the grid 18. Between cathode 17 and the plate 19 is an accelerating plate potential which draws the l secondary electrons, which yare controlled by the grid 18, to the plate. The lead-in for the plate potential required by the first system can be effected at 21. At the same time, similarly as above described, control of grid 15 can be effected by the potentials amplified in the first triode or multiple electrode system 17, 18, 19. Also in this manner, cold and hot cathodes can be combined in 'such a manner that thermo-electric heating will be required only 'in the last-stage or last triode or multiple electrode system.

It is evident that the building of multiple` unit tubes is substantially simplified if only a single hot vfilament has to be provided` that is, for the last .stage or ceding stages are excited by cold cathodes so that these cathodes require but one lead- 1n.

As shown in Figure'l, the electron sup lead need not be brought to the outside, indeed, it may be 'run inside the tube itself. Multiple-unit tubes do not exhibit any apsystem, and all preply recaer? preciably larger consumption of heating and plate current than the last-stage system alone.

Vlfor example, if the tube comprises three ampliier systems, two of which are being run with cold cathodes as hereinbefore described, and the last stage is operated thermo-electrif cally the saving realized in heating and plate current will be apparent. itisa also clear that this is-a radical and decided step forward in the art of building radio tubes. l l

' lt may be also mentioned that the arrangement according to Figure 2, although intended 'for the utilization of secondary electrons, represents an arrangement also suited Jfor photo-electric operation. if desired, both the photo-electric action as well as the generationof secondary electrons may be comn bined. Indeed, this result will be readily obtained it `the light produced by the lilament 14- is allowed to act directly upon the surface of the cathode 17 and if in addition primary electronsoriginating from thefilament 14, are allowed to directly impinge upon the cathode 17 with the result that secondary electrons are generated.

Having thus described my invention what I claim is:

. control electrode, and c i. A multi-stage ampliier tube housing an end triode system having an anodeand a cathode adapted to emit electrons and light, i

and a preceding triode system having a cathode independent of said first cathode and anode and adapted to emit electrons by virtue` of the luminous emission from the cathode of the end triode system.

2. An ampliiier comprising a plurality of independent triode systems, one of the systems having a cathode adapted to emit electrons when heated, a cathode in another system independent of said first 'system adapted to emit electrons when exposed to light rays,

said systems being enclosed by' a singlev vessel.

n amplifier comprising a plurality of Y triode systemsl confined within a single ves.

sel, light responsive means in one `of the systems and means on-the surface of the vessel to concentrate light on the light responsive means.

4. An evacuated end stage and a preceding stage, each of said stages including an anode, coltrol electrode, and a cathode, lightfresponsive means on the cathode in thel preceding1 stage,"the anode,

ing stage being inde endent of the anode, control electrode an and including an anode and cathode, the

amplifier tube housing an j. cathode of thesecond theionic device on iid' 0de, and a preceding triode system having a' photo-electric cathode.

8. A. multi-stage amplier tube housing an end multiple electrode system including an anode and cathode wherein electrons are emitted from said cathode, a preceding multiple electrode system including a cathode independent of said rst cathode and anode,

' and means on said second cathode whereby uthe electron emlssion of said` preceding system is caused photo-electrically by light, trom said end sta e.

9. In com ination, a tube, a plurality of independent triode systems disposed in said tube, each system including a cathode, and means whereby the electron emission :[rom

one of the cathodes is caused by light emitted from the other cathode.

10. In combination, anamplifier tube comprising, a plurality of; multiple electrode systems, one of said systems being an end stage and having a heatable cathode,l and another of said systems being a precedingstage and having a cold cathode, the'latterbeing provided with light responsive coating whereby emissions from bthe heated cathode czuse electron emission rdni the cold catho e.

sinonimi) Loewe. fm.

ode in the precedl.

cathode-in the end cathode being provided with a photoelectric coating, asecond thermionic device disposed in said container and including an anode and a cathode, and means on'the surfaceofithe container to concentrateA light from the 'lao' 

